1. Field of the Invention
The present invention generally relates to image forming techniques and, more particularly, to an image forming apparatus such as a copy machine, a printer, a facsimile machine, etc., and an image reading apparatus that is mounted on such an image forming apparatus.
2. Description of the Related Art
Generally, as a reading means (reading sensor) used for an image reading apparatus, there is a method of reading an original document S by a reading sensor 101 having a length covering an entire width of the original document S such as shown in FIG. 1A and suggested in Japanese Laid-Open Patent Application No. 2003-8831. This method of reading can easily acquire a high-quality image, but there is a problem in that a length covering the entire width of the original document S is required for the reading sensor 101, which increases a cost of the reading sensor 101.
In order to solve the above-mentioned problem, there is suggested, as shown in FIG. 1B, a reading arrangement in which a plurality of reading sensors 101 are located in a staggered arrangement so as to shorten the length of each of the reading sensors 101 to reduce a cost of the reading sensor.
It should be noted that, besides the reading sensor arrangement mentioned above, there is an image reading arrangement, such as shown in FIG. 1C, in which a reducing lens 105 is arranged between a contact glass and each of the image reading sensors 101.
Although the method shown in FIG. 1B can reduce a cost and also reduce an image reading apparatus, there are problems in that positions of the reading sensors tends to shift due to thermal expansion and complex image processing must be applied such as an image synthesizing process after an image is read by each reading sensor.
In order to solve such a problem, there is suggested an image reading apparatus suggested in Japanese Laid-Open Patent Application No. 5-336301. The image reading apparatus disclosed in this patent document has a structure in which image sensors located in a staggered arrangement on a base member are movably supported by a spacer in a longitudinal direction and adjacent two image sensors are connected to each other by a connection member. For this reason, even if a base member expands and contracts due to changes in an environmental temperature, a positional relationship between ends of the two image sensors adjacent to each other, thereby preventing a shift in the read image due to the changes in the environmental temperature.
However, since the image reading apparatus disclosed in Japanese Laid-Open Patent Application No. 5-336301 uses adhesive or screws to fix the reading sensors to the connection member, positions of the reading sensors may be shifted, when fixing the reading sensors, due to an external force during a screw-fixing operation or a contraction of an adhesive during a curing process, which may result in a shift in an image read by the thus-fixed read sensors.
Moreover, since an adjustment is needed to accurately arrange the reading sensors before fixing the reading sensors to the connection member, there is a problem in that an adjusting mechanism for accurately positioning the reading sensors becomes complicated.